First I will start with the box. I wanted to retain all the storage space possible in my terrain, so I decided to build a factory drop in, much like the JL Audio version.

Factory Sub Removal: What I did was removed the entire rear interior panel. First take off the plastic covers and remove the bolts for the 4 cargo clips (2 on each side). I also took the plastic piece around the trunk latch off ( just pops up) as well as removed the trunk cover. I had to pull the rear seat all the way forward, but then the rear panel just pops off. I found it easier if you pull the bottom out, which caused the top clips to pop out. There are 10 clips along the top and then 3 or 4 white push in clips towards the bottom/passenger side door. From here the subwoofer was pretty easy, 4 10m bolts, 2 top, 2 bottom, release the clip for the wires and pull it out. I put my amp on the driver's side, since there is nothing behind that panel, so repeat the same exact process for interior removal if you choose to do so.

Essentially the whole box is MDF, but the back is fiberglass to fit into the hole better. I then covered the entire factory subwoofer in plastic and duct tape. I then laid a layer of fiberglass to make a mold of the back side. After letting it dry, I removed the fiberglass mold from the subwoofer and laid another layer of fiberglass to make sure it was strong. After that I traced out the top and bottom and cut a pieces out of MDF. Once I cut them, I clamped them in place and measured what size the front needed to be. I then cut the front piece out of MDF, including my sub hole and terminal cup. I then screwed together my top, bottom and wood pieces as well as a couple inside support beams to ensure it was strong. Then I took the MDF piece and placed it inside the fiberglass mold. I started by using gorilla glue and clamped it all together. Then I used some Bondo Glass mix, basically bondo, with fiberglass chunks in it. I used this to fill every butting corner, and by that, I mean any surface touching another surface, whether it is wood to wood, or fiberglass to wood. It was all covered in bondo glass to seal everything. I also used bondo glass on the outside, because my MDF cutouts were a little off from fiberglass mold. Once the box was completely sealed and solid, I added 2 more layers of fiberglass, bringing me to around 3/8" of glass around. I figured it should be good enough considering most of the box is MDF. Then I took a stupid amount of resin and coated the entire thing again just to add another layer of harness as well as smooth out the entire box. I sanded down all the edges and then bondoed spots that were still a little rough, although I didn't have to do that even since it is hidden. Then sanded to the bondo to make the whole box smooth. To make it look legit, I also covered it in grey fleece, spraying it in 3m spray glue. But again, its hidden, nobody will ever see it. Here are a couple pictures showing the box support, bondo and covered.

Installation:
The hardest part of the entire install was deciding how to run the power wire! I looked everywhere and could not find a place to get to the get to the battery and I refuse to run a power wire on the outside and refuse to drill any holes. What I ended up doing is running the power wire under the trim from the driver's side rear quarter panel where the amp is all the way to the battery. Remove the 2, 7m screws holding on the panel under the steering wheel. Then remove the 4, 10m bolts holding on the metal cover. To get through the firewall, I pushed out the rubber seal that holds in the hood latch wire. It was so tight of a squeeze I didn't even bother putting silicone in the tiny gap left over. Remove the plastic cover on the battery by sliding it towards the outside of the vehicle. Then remove the top computer (ecu) by removing the 10m bolt on the left side of the battery and slide towards the outside of the vehicle. Here in the picture is what I used to secure the power wire to the battery.

The negative was easy, you will notice when you pop off the driver's side rear quarter panel interior piece of all the little bolts coming out to put a O terminal ring on. There is probably 4-5 places to choose from so your wire can be pretty short.

There really isn't a good place to hook the remote wire switch to in the back of the car, so I ran it along the driver side under the trim again like the power wire. Note: Rear cigarette lighter is hot all the time, and cannot be used for the remote switch. However, under the back seat I turned the remote wire towards the rear center console cigarette lighter. Pop this panel off by just pulling outwards. I had to pull and use a screwdriver to make sure I didn't damage anything. Then I just spliced it to the switched hot wire, the hot one I believe was blue? Not 100% but I know it's the wire that is not black.

I took the harness from the subwoofer and cut it so I could use it to hook back into the factory wiring and would not have to cut up any factory wires. I also cut it in a place where if I wanted to put the factory sub back in some day, I could. I then wired the my line out converter to the wires and hooked it back into the factory harness for the subwoofer. Pretty simple. 2 positive wires, 2 negative wires have stripes and the wiring on the subwoofer is even easier with red and black. I then ran RCA's to the amp input and set the amp to receiving a low input signal since I was using the factory subwoofer harness. Use the high input if you're running it from the front or rear speakers. The speaker wires I simply ran along the back of the car around the spare tire.

Last thing, some people won't have this but my kicker amp has a remote knob switch to turn the bass up and down. You could just set it at a low level and not worry about it but I like the ability to turn it up and down if I want while driving. I should have took a picture of this but I didn't. I ran the wire along the driver's side trim again, along the power wire. Right under the steering wheel on the trim there is a little section that comes down for some reason. I took the knob apart and used washers covered in the same gray fleece as the sub to secure it and hide it. This way I didn't even have to drill a hole in the vehicle.
Here are the couple pics I took with everything in place. It sounds awesome and hits way better than that factory "subwoofer". I should mention this is on a 2012 Terrain 6cyl. Not completely sure about the wiring for ANC on the 4 bangers.

Comments or suggestions are welcome as well as any flamers out there. Also any clarification on anything just ask as I was pretty vague with much of the install.

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